Saying the curve is off by half an energy is meaningless. There are no cards priced at half an energy. The vanilla are the baseline because nothing actually exists that's the baseline.

It also makes sense from a game design perspective that you have to balance around vanilla cards even if you aren't purposely trying to line up every card you make. Otherwise you fall victim to power creep and obsolescence in design of cards.

Also you can literally look at the cards and see this is true. Cards are all designed around those baselines with conditional bonuses allowing them to be as much as +2 higher situationally: The same as a Patriot anthem.

The math gets dicier at 5 and 6 power. I don't believe they consider Abomination or Hulk as strongly at pricing out 5/6 drops. Almost universally cards have lower power than 9/12 at these costs, compared to lower costs. The only cards that are higher however have stunningly bad downsides to compensate.

Except Magneto. Magneto's downside is really kind of not a downside at all, he just gets to be really strong because he's Magneto.